The Department of Homeland Security’s Cyber Security Assessments of Industrial Control Systems (DHS) provides an overview of the assessment process so users understand how to execute an ICS cyber security assessment. This guide also covers the process of planning an ICS cyber security assessment, including how to select testing areas. The test plan specifies the correct amount of detail to meet the needs of the asset owner while retaining the flexibility to use all the skills of the assessment team. The details of the actual testing process in this guide familiarize the asset owner with the steps and reasons behind the testing process. The reporting process for an ICS cyber security assessment is also covered in this guide.